Good character development, interesting OCs, and interesting worldbuilding. Shame that the worldbuilding doesn't fit too well with the consequences and that it follows the stations of canon a little too well, but I suppose that's not what this fic set out to do.
Still my favorite Ginny-centric fic.

Changeling disappointed me. Not because the fic is bad, not because I've expected more going into it. It's because after reading it, I've seen that it could be more, but it wasn't.
It's hard for me to write about The Changeling without comparing it On the Way to Greatness, so I won't even try. The similarities between the two are obvious, both are staying pretty close to canon "X in Slytherin" fics focusing mostly on characterisation.
But there are also differences, while one of my problems with OtWtG is that the first chapters are too long, with Changeling there are many moments that I feel that they are too short. It really shows when we come to Ginny's sixth year when it becomes obvious that some characters (mainly Parlour Girls) could use more prior characterisation.
There is also a big difference in what "staying close to canon" is for both fics. While in OtWtG there is a lot of painful railroading story back into known tracks, the events often unfolded differently, have different consequences. If the end of the fic will come one day, it won't be the same as the original books (unless we get absurd cop-out). That is obvious since the end of the fourth year.
With Changeling it is different. The events stay the same, even though they clearly shouldn't. It's not noticeable for the first three years, Ginny didn't have much influence of those. But in the fourth year, we have Department of Mysteries. And everything goes exactly the same way. Despite there being one person more here, despite Ginny's completely different mindset. Sirius dies the same way, Ron gets attacked by the brains, everything is the same. This gave me premonition that nothing will change during Battle of Hogwarts. And it didn't. Despite additional intel, despite different defenders, despite the Box, everything ended the same way. The same people died, nothing changed. That clashes terribly with the theme of some actions being "necessary" despite their price. If the results are the same, then this was all for nothing. Unnecessary.
I've mentioned the Box, and this also ties in what I said about some characters needing more space. We knew that she was good, but we didn't know she was that good. It felt like a cheap plot device. Or rather it would felt like a plot device if it actually affected the plot.
Speaking of cheap plot devices, the "female magic" also was a terrible way to have Ginny learn occlumency quickly. I also didn't really bought the limited education of females. It doesn't make settings with the settings of the original books, and no changes were introduced that would make it make sense here.
Still, despite all my complaining, it's a good fic, and one definitely worth a read. 7.5/10

The way this story stands out to me is the way it handles the Harry Potter cast in general, in that it has an excellent handle on each and every character. Every person is pretty much their canon self. Malfoy, Snape, Fleur, the Weasley's, they're are all perfectly in character. I think this is also pretty much the most perfect depiction of Draco Malfoy that I have yet to see in fanfiction. He is exactly as he is in the books, no dumber and no smarter. Ginny, of course is changed but not in a way that replaced her character with someone else entirely but rather that she is still Ginny, only changed through her different life experiences in an organic manner.
I didn't mention Harry, because him I felt the one changed the most, but also in a good way. With Ginny being a different character and thus actually a bigger influence on him did allow for some genuine changes in his character and an openness to reflect on himself and others in a different way than before. He is still a good character and distinguishably himself but a bit more developed.
The OCs, speak all the Slytherins and some Ravenclaws I actually really enjoined.
Ginny has two friend-groups in Slytherin, one being her two best friends Smita and Tobias and the other being the girls of the parlor and I find that while the latter group may not have been developed as much as I would have liked, I still appreciated each and every character.
The Parlor was something that I also loved. It's a clever invention, one that feels particularly fitting into the Harry Potter mythos and works exceedingly well in the story as it serves to explore Ginny's characters in a multitude of ways, as both a regular member desperately seeking advice, companionship and a place to belong and later as a leader who is responsible for each and every single individual in it and is probably the thing I am looking forward the most in the third story, to see Ginny trying to rebuilt the Parlor, to invite new girls into it and see on whom she will ultimately pass the torch to.
In general this has been a great story exploring Slytherin, one of the best I have seen in fanfiction to do that. There is no Slytherin wank, no bashing. Slytherin is not a "pit of snakes". It's not Game of Thrones with schoolchildren where every character is Littlefinger, Varys or Cersei. No senseless scheming or arbitrary ranks or whatnot. They are just kids for the most part, but it is still distinguishable from the rest due to its unique nature.
As a whole, Ginny has been an excellent character to use for this, genius even. Since she is a year younger, the story gives us a new cast to play with and at the same time, removes her from canon events enough that the focus is always on her journey and not necessarily derailing the plot, although the canon elements are still happening in the background and shaping her life. Ginny finding her place in Slytherin has been a gripping journey, one told expertly with not a spelling mistake in sight and with smart stylistic choices.
For example, I loved that her first year was basically a haze, as both her worldview being shaken and being controlled by Riddle had a tremendous impact on her, one that she couldn't shake for a while.
It was carving her own space with Quidditch, the life-line that the Parlor threw her and making friends with Tobias and Smita that ultimately allowed Ginny to get on her feet and finally claim her place in Slytherin, which was, on a whole, really satisfying to read.
Ron dressing in Slytherin colors to cheer on his sister was also one of the more heartwarming moments in HP fanfiction that I've seen in a while. It deserves mention that I also loved how her family reacted to her being in Slytherin, how they tried but their prejudices would get in the way at times and say thoughtless things but which they also ultimately were able to overcome.
As to the negatives, I guess I agree that there could have been a bit more characterization on the Parlor girls, although I guess that will come in the third story. Still, some more distinction among the girls outside of what they pursue wouldn't have hurt. And while I appreciated the story not having Ginny derail the plot by overtaking it, as this is very much a Slytherin Ginny story and not a Dark Lady Ginny story, I have to admit it's a bit weak that Ginny's influence on Slytherin hasn't really altered anything so far. Sure, I guess there will be a slightly more positive perspective on Slytherin as a whole, especially in the younger years, but the fact that Ginny and the additional Slytherins who stayed had virtually no impact on who died and who didn't is a bit weak.
I liked that the Slytherins faced stark consequences for their bravery. There was death, injury and fallout from that, stuff that the second story explores in an interesting manner, only that the impact is really only felt by them, not by the plot at large, if that makes sense. Their impact is restricted to them alone, not the larger picture. Could have led to more or less deaths of canon, something like that. Make things better or worse and not have them stay exactly the same. Looking back, that is really disappointing.
Snape (and I don't think there is any chance of Ginny naming any of her children after him, if they have any) has been handled really tastefully, I have to say. Also rather in character, he hasn't been glorified or bashed. Instead, there was nuance in the way the story used him and different characters saw him differently and all for good reasons
Characters in general haven't been whitewashed, the Malfoy's being great examples of that. Even after their turn, they didn't do a 180 but rather remained their slightly antagonistic, aloof selves who aren't suddenly super regretful and nice but rather awkward, distanced people who don't quite know what to do.
I think, ultimately, that is the greatest strength of this story. It is so very grounded and mature that it never overextends itself and knows exactly what it is it wants to do and then efficiently does it. This is not a story that has been written on the fly but rather was meticulously planned and edited and the effort is shown and has paid off in every line.
It has its flaws but nothing at all game-breaking and if you at all like Harry Potter fanfiction and the wizarding world, you owe it to yourself to at least check it out.

I know this is supposed to be a character analysis but I could never get over the fact the fic, despite all the differences entailed by Ginny being a Slytherin, still follows all of the stations of canon.

Easily one of the best fics out there. Ginny is an interesting character to follow, and her friends are very unique and fun. Yes, a lot of this is a rehash but it feels realistic, and Ginny has her own plot points within the years. The writing is amazing.